In accordance with a rapid spread of information relevant apparatuses and communication apparatuses such as a personal computer, a video camera and a portable telephone in recent years, the development of the battery to be utilized as a power source thereof has gained recognition. The development of the high-output and high-capacity battery for an electric automobile or a hybrid automobile has been advanced also in the automobile industry.
The battery having an electrolyte and a pair of electrodes holding the above-mentioned electrolyte therebetween is used as such a battery. Further, metallic lithium and a sulfide-based solid electrolyte have been widely used as a material composing the electrodes and the electrolyte.
However, the above-mentioned metallic lithium and sulfide-based solid electrolyte have properties of reacting with water, and the problem is that heat is generated by contacting with water and performance is deteriorated in accordance with the generation of hydrogen sulfide.
To respond such a problem, in the field of an air battery using oxygen as a cathode active material and metallic lithium as an anode layer, a method for restraining metallic lithium from contacting with water by using as an electrolyte a hydrophobic nonaqueous liquid electrolyte, which transmits oxygen and water with difficulty, is disclosed (Patent Literature 1).
In the field of a sulfide-based solid state battery comprising a solid electrolyte layer having a sulfide-based solid electrolyte, a method for coating a power generating element comprising the above-mentioned solid electrolyte layer and a cathode and an anode for holding this therebetween with an ionic liquid is disclosed in Patent Literature 2.
In order to improve the air tightness of the battery, a method for using a predetermined gasket material is disclosed in Patent Literature 3.
Further, Patent Literature 4 discloses a lithium battery comprising a cathode laminated body and an anode laminated body, in which the cathode laminated body and the anode laminated body are laminated, and an intervention layer made of an ionic liquid between both of the laminated bodies for the purpose of improving the adhesion properties of the above-mentioned two laminated bodies.
However, the above-mentioned hydrophobic nonaqueous electrolyte used in the above-mentioned Patent Literature 1 is liquid in the use temperature of the battery for the reason that the melting point thereof is 60° C. or less. Thus, even though the hydrophobic nonaqueous electrolyte has a hydrophobic property, moisture may not be prevented from mixing in and water mixes into the electrolyte (liquid) with the passage of time. Accordingly, in the method using the above-mentioned hydrophobic nonaqueous liquid electrolyte, the problem is that moisture may not sufficiently be prevented from mixing in.
The ionic liquid used in the above-mentioned Patent Literature 2 is liquid, so that water necessarily mixes in by the distribution coefficient of water, and the problem is that moisture may not sufficiently be prevented from mixing into the above-mentioned solid electrolyte layer. Further, the solid electrolyte layer is soaked in the ionic liquid having no ion used for the battery, such as Li+ in a lithium battery, Na+ in a sodium battery and Ca2+ in a calcium battery, so that there lies a problem in that the properties of the battery are deteriorated due to resistance increase caused by mixing in of the ionic liquid. In addition, an ionic liquid having chloroaluminate and tetrafluoroborate has been used as the ionic liquid used in the above-mentioned Patent Literature 2, and there is a problem in that these are inappropriate as a material for preventing moisture from mixing in by reason of having a hydrophilic property to promote the mixing in of moisture.
In the method disclosed in the above-mentioned Patent Literature 3, the problem is that it is difficult to completely restrain moisture from mixing in and no effects are exhibited in the case where moisture mixes in during production.
Further, the ionic liquid used in the above-mentioned Patent Literature 4 is liquid as described above, so that the problem is that water may not sufficiently be restrained from mixing in, similarly to the above-mentioned Patent Literature 2.